U.S., South Korea, Japan seek to raise pressure on North's nuclear program

SEOUL (Reuters) - The United States and two key Asian allies discussed how to increase pressure on North Korea to halt its nuclear program and will urge China to help bring Pyongyang back to the negotiating table, officials said.

The talks in Seoul follows a test of what the North said was a submarine-launched ballistic missile earlier this month, which if true, could mean progress in the reclusive state's military capabilities.

"We held specific discussions on ways to deter North Korea's provocations and increase the effectiveness of sanctions," South Korea's chief nuclear negotiator Hwang Joon-kook told reporters after meeting envoys from the United States and Japan.

North Korea has been hit with UN and U.S. sanctions because of its nuclear and missile tests, moves that Pyongyang sees as an attack on its sovereign right to defend itself.

Hwang said the North's test of its submarine-launched ballistic missile system was clearly a violation of U.N. Security Council resolutions.

U.S. Secretary of State John Kerry said last week that Washington and Beijing were discussing imposing further sanctions on North Korea, which he said was "not even close" to taking necessary steps to end its nuclear program.

Sung Kim, U.S. representative to so-called six-party talks hosted by China and aimed at reining in North Korea's nuclear ambitions, said he would meet Chinese officials this week to seek ways to resume the dialogue.

"In a sense, they (North Korea) have given us no choice but to cooperate on enhancing pressure on North Korea," he told reporters.

"I think the Chinese understand as chair of the six-party process, they have a special responsibility to get the North Koreans to work with us towards denuclearization," he said.

North Korea, which regularly threatens to destroy the United States, walked away from a 2005 deal with China, Japan, Russia, South Korea and the United States to end its nuclear program in return for diplomatic and economic rewards.

Then in 2012, weeks after signing a deal calling for a moratorium on nuclear and long-range missile tests, the North launched a ballistic missile, effectively voiding the agreement, which had also promised U.S. food aid to the impoverished state.